1. Field of the Invention
The invention relates to a magnetic separator particularly for the removal of ferromagnetic particulate material loaded with contaminants.
2. The Prior Art
It is well-known that liquids contaminated with suspended particles or dissolved high-molecular substances, such as resinous substances, can be cleaned by adding a ferromagnetic particulate material, such as magnetite, iron, cobalt or nickel, to the liquid and separating the contaminant together with the ferromagnetic material in a magnetic field. It is also known to clean liquids in a similar way, which liquids from the start contain contaminants of ferromagnetic particulate materials, for example departing coolant from machines for mechanical machining, such as lathes and drills. Also contaminated gases can be cleaned in principle by the addition of a ferromagnetic particulate material and treatment in a magnetic field for separation of the contaminants. It is also known to use chemical flocking agents simultaneously in the cleaning process, for example lime, alum, iron chloride, polyelectrolytes and water glass.
In the described cleaning operations a magnetic separator is used. One known embodiment of such a separator consists of a rotatable cylindrical drum which is lowered down into a trough which is concentric with the drum, so that a gap is formed between the envelope surface of the drum and the trough. A plurality of permanent magnets are arranged in longitudinal rows on the inside of the envelope surface of the drum, and the medium to be cleaned is lead through said while at the same time the drum is rotated. The separator is also provided with a scraper for removing the material which adheres to the drum during the separation so that the process is continuous. The magnets can either rotate with the drum or be stationary during the rotation of the drum.
Another known embodiment of a magnetic separator is formed with a gap between two plane parallel rigid walls, one of which contains a plurality of horseshoe magnets built into it and located adjacent to and spaced from each other.
Proposals have also been made to provide magnetic separators, the walls of which consist of ferromagnetic material and are attached, radially directed, along a rotatable shaft, the separator being provided with a stationary magnet with the ability to generate a magnetic field, substantially parallel with the rotatable shaft, with local gradients. To achieve a practical embodiment of such a separator, space-demanding and very expensive magnetization devices are required, such as an iron circuit and a magnetization coil. The scraper means may be of a finger-like type.